A brush type D.C. motor comprises a stator having arcuately shaped permanent magnets distributed around the stator's circumference to create alternating magnetic poles. These magnets provide magnetic flux patterns that interact with commutated electric current flow delivered via brushes to windings disposed on the motor's armature to produce armature shaft rotation.
A brushless type D.C. motor may be considered to comprise a stationary part, the stator, and a rotary part, the rotor. Windings are typically on the stator, and magnets on the rotor. There are several different configurations for a brushless, electronically commutated D.C. motor. In one, the rotor is disposed in circumferentially surrounding relation to the stator, with an intervening radial air gap between the two; in another, the stator is disposed in circumferentially surrounding relation to the rotor, with an intervening radial air gap between the two; and in yet another, the stator and rotor are axially confronting, separated by an axial air gap. In these configurations, the current flow to the windings is electronically commutated, rather than being commutated by mechanical commutators and brushes.
A known form of stator comprises winding slots that are spaced circumferentially around its perimeter. The slots are open in the radial direction and they are parallel to the rotor axis of rotation, being also open at their axial ends. In a motor configuration where the stator surrounds the rotor, the slots are open radially inwardly while in a motor configuration where the rotor surrounds the stator, the slots are open radially outwardly. Windings are disposed in these slots in predetermined winding patterns that will produce shaft rotation when they are energized in proper sequence by electronic commutation.
The present invention relates to a novel winding configuration that is especially, although not necessarily exclusively, useful in a permanent magnet brushless D.C. motor. In the disclosed exemplary embodiment, the invention comprises a five phase stator winding containing five individually commutated windings. Permanent magnets of the rotor provide three magnetic poles pairs wherein each pole pair spans essentially 120.degree. (mechanical) of the rotor circumference.
Generally speaking, the invention relates to a D.C. motor comprising an rotor and a stator circumferentially separated from each other by an air gap, one of the stator and the rotor providing magnetic flux paths across the air gap for interaction with the other of the stator and the rotor, the other of the stator and the rotor comprising multiple phase windings, means for selectively connecting the phase windings in sequence to a D.C. electrical source, wherein each phase winding is energized for a certain span of rotor rotation, and during an initial portion of that span, the immediately preceding phase winding is simultaneously energized, and during a final portion of that span the immediately succeeding phase winding is energized. The invention is further characterized in that at any given time, only two of the phase windings, and no others, are being simultaneously energized.
Principles, and various features and advantages, of the invention will be presented in the following detailed description that is accompanied by drawings representing the best mode contemplated at this time for carrying out the invention.